This invention relates to the pouring of molten metals from a ladle into a receiving vessel such as a mold or a tundish of a continuous casting facility. It relates particularly to improvements in the construction of a sliding gate molten metal valve commonly used to control the flow of molten metal from the bottom of a ladle or tundish.
Sliding gate molten metal valves generally are comprised of a stationary upper plate having an orifice, a reciprocable lower slide plate having an orifice and movable in contact with the underside of the upper plate to bring the orifices in the two plates in and out of registry with each other to open and close the valve. A discharge nozzle is mounted below the lower sliding plate in alignment with the lower plate orifice to direct the molten metal into the mold or tundish.
While the lower slide plate is held tightly against the underside of the upper plate with springs, it has been noted that air is capable of being drawn into the orifices in the plates and causes oxidation of the molten metal as it is being discharged through the sliding gate valve. If the molten metal is aluminum-killed steel, the aluminum in the steel will be oxidized forming particles of alumina which adhere to the discharge nozzle or remain in the steel as harmful inclusions.
Past attempts to prevent the infiltration of air into the sliding gate valve or by flooding the area around the plates have not been successful in preventing the infiltration of air into the plate orifices.